Charged particle beam writing apparatus, charged particle beam writing method and recording medium

1. A charged particle beam writing apparatus comprising: a charged particle beam source; a deflector adjusting an irradiation position of the charged particle beam with respect to a substrate placed on a stage; a shot data generator generating shot data from writing data, the shot data including a shot position and beam ON and OFF times for each shot; a drift corrector referring to a plurality of pieces of the generated shot data, calculating an amount of drift of the irradiation position of the charged particle beam with which the substrate is irradiated, based on the shot position and the beam ON and OFF times of each of a plurality of shots, and generating correction information for correcting an irradiation position deviation based on the amount of drift; a deflection controller controlling a deflection amount achieved by the deflector based on the shot data and the correction information; and a dummy irradiation instructor instructing execution of dummy irradiation in a writing process to irradiate with the charged particle beam in a predetermined irradiation amount at a position different from the substrate on the stage.

2. The charged particle beam writing apparatus according to claim 1, wherein the dummy irradiation instructor instructs execution of the dummy irradiation at predetermined timings or at each occurrence of an event.

3. The charged particle beam writing apparatus according to claim 2, wherein the dummy irradiation instructor calculates an electric discharge amount during a time not used in the calculation of the amount of drift, and determines the irradiation amount of the dummy irradiation based on the electric discharge amount.

4. The charged particle beam writing apparatus according to claim 1, wherein the deflector includes a plurality of electrodes, and the drift corrector calculates an amount of accumulated electric charge of each of the plurality of electrodes based on a total of a beam ON time, a total of a beam OFF time, an average deflection direction and an average shot size of the plurality of shots, and calculates the amount of drift from the amount of accumulated electric charge of each electrode.

5. A charged particle beam writing method comprising: discharging a charged particle beam; adjusting an irradiation position of the charged particle beam using a deflector with respect to a substrate placed on a stage; generating shot data from writing data, the shot data including a shot position and beam ON and OFF times for each shot; referring to a plurality of pieces of the generated shot data, and calculating an amount of drift of the irradiation position of the charged particle beam with which the substrate is irradiated, based on the shot position and the beam ON and OFF times of each of a plurality of shots; generating correction information for correcting an irradiation position deviation based on the amount of drift; controlling a deflection amount achieved by the deflector based on the shot data and the correction information; and executing dummy irradiation in a writing process to irradiate with the charged particle beam in a predetermined irradiation amount at a position different from the substrate on the stage.

6. The charged particle beam writing method according to claim 5, wherein the dummy irradiation is executed at predetermined timings or at each occurrence of an event.

7. The charged particle beam writing method according to claim 5, wherein an electric discharge amount during a time not used in the calculation of the amount of drift is calculated, and the irradiation amount of the dummy irradiation is determined based on the electric discharge amount.

8. The charged particle beam writing method according to claim 5, wherein the deflector includes a plurality of electrodes, and an amount of accumulated electric charge of each of the plurality of electrodes is calculated based on a total of a beam ON time, a total of a beam OFF time, an average deflection direction and an average shot size of the plurality of shots, and the amount of drift is calculated from the amount of accumulated electric charge of each electrode.

9. A computer readable recording medium storing a program causing a computer to execute a process comprising: discharging a charged particle beam; adjusting an irradiation position of the charged particle beam using a deflector with respect to a substrate placed on a stage; generating shot data from writing data, the shot data including a shot position and beam ON and OFF times for each shot; referring to a plurality of pieces of the generated shot data, and calculating an amount of drift of the irradiation position of the charged particle beam with which the substrate is irradiated, based on the shot position and the beam ON and OFF times of each of a plurality of shots; generating correction information for correcting an irradiation position deviation based on the amount of drift; controlling a deflection amount achieved by the deflector based on the shot data and the correction information; and executing dummy irradiation in a writing process to irradiate with the charged particle beam in a predetermined irradiation amount at a position different from the substrate on the stage.